Journal of Lipid Research, Vol 32, 1417-1427, Copyright © 1991 by Lipid Research, Inc.
Bile acids of marsupials. 2. Hepatic formation of vulpecholic acid (1 alpha,3 alpha,7 alpha-trihydroxy-5 beta-cholan-24-oic acid) from chenodeoxycholic acid in a marsupial, Trichosurus vulpecula (Lesson)
J St. Pyrek, SP Lee, L Thomsen, C Tasman-Jones and B Leydon
Life Sciences Mass Spectrometry Facility, College of Pharmacy, University of Kentucky, Lexington 40536-0082.
Free vulpecholic acid (1 alpha,3 alpha,7 alpha-trihydroxy-5 beta-cholan-
24-oic) is the major biliary component of the Australian opossum
(Trichosurus vulpecula), accompanied only by a few percent of its taurine
conjugate. In order to exclude a microbial involvement in its formation
(i.e., secondary origin) four sets of experiments were performed. It was
found that a) the level of vulpecholic acid remained unchanged in the bile
of opossums fed with neomycin and kanamycin for 7 days prior to bile
collection; b) it also remained unchanged after long bile drainage; c) in
opossums prepared with biliary cannula, intraportally injected
[24-14C]chenodeoxycholic acid was transformed to [24-14C]vulpecholic acid;
and d) in a similar experiment, the detectable transformation of [1 alpha,2
alpha-3H2]cholesterol to vulpecholic acid was observed. In experiment c)
28-66% of the administered radioactivity was secreted in 2 h in the form of
free biliary vulpecholic and chenodeoxycholic acids. Only a trace amount of
the corresponding taurine conjugates (approximately 0.4%) was formed.
Moreover, rapidly declining specific radioactivity of the unconjugated
chenodeoxycholic acid indicated its probable participation in the native
formation of vulpecholic acid.
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